package sigletondemo;

public class Student {
    public static void main(String[] args){
        Principal principal1=Principal.getPrincipal();
        principal1.announcement("明天放假");
        Principal principal2=Principal.getPrincipal();
        principal2.approveDocument("图书馆关闭");
        System.out.println("这些消息是同一位校长说的吗: "+(principal1==principal2));
    }


}
